The present invention relates to scaffold fixation devices useful in articular cartilage repair and more specifically to a device for fastening an articular cartilage scaffold to underlying bone.
Articular cartilage is a tissue that covers the articulating surfaces between bones in joints, such as the knee or elbow, which is subject to catastrophic or repetitive stress injury. Various means have been proposed to address such injuries including repair via tissue engineering. Tissue engineering is defined as the application of engineering disciplines to either maintain existing tissue structures or to enable new tissue growth. This engineering approach generally includes the delivery of a tissue scaffold that serves as an architectural support onto which cells may attach, proliferate, and synthesize new tissue to repair a wound or defect. Surgical use of a tissue scaffold requires a fixation means to secure the scaffold to the bone beneath the wounded cartilage site. Secure fixation of the scaffold within the wound site is necessary for proper healing.
Frequently, scaffolds, prostheses and fasteners used in orthopedic applications are made from synthetic absorbable biocompatible polymers which are well known in the art. Such polymers typically are used to manufacture medical devices which are implanted in body tissue and absorb over time. Synthetic, absorbable, biocompatible aliphatic polyesters include homopolymers, copolymers (random, block, segmented and graft) of monomers such as glycolic acid, glycolide, lactic acid, lactide(d, l, meso and mixtures thereof), xcex5-caprolactone, trimethylene carbonate and p-dioxanone. Numerous U.S. Patents describe these polymers, including U.S. Pat. Nos. 5,431,679; 5,403,347; 5,314,989 and 5,502,159. Devices made of an absorbable material have the advantage that they are absorbed by the body after healing has occurred.
U.S. Pat. No. 5,067,964 describes an articular cartilage repair piece which includes a backing layer of non-woven, felted fibrous material which is either uncoated or covered by a coating of tough, pliable material. A number of means are disclosed for fastening the repair piece to the underlying bone. U.S. Pat. Nos. 5,306,311 and 5,624,463 describe a prosthetic, resorbable articular cartilage and methods of its fabrication and insertion. U.S. Pat. No. 5,713,374 describes an attachment method to hold a biomaterial in place until healing occurs. U.S. Pat. Nos. 5,632,745 and 5,749,874 and 5,769,899 describe a bioabsorbable cartilage repair system.
It is well know that there is wide variability in stiffness, strength, and other physical properties of human bone, and that the properties vary from site to site among humans. It is therefore challenging to design mechanical fasteners for fixing a prosthetic scaffold to bone because the mechanical function of the device must be able to accommodate a range of bone physical properties.
Accordingly, it would be advantageous to provide a scaffold fixation device which has a fixation means that can perform in a variety of human bone.
The limitations of prior art devices for attaching a tissue scaffold to bone tissue, are overcome by the present invention which includes an attachment device having a platform positionable in substantially parallel relationship to the bone tissue for retaining the tissue scaffold proximate to the bone tissue. A post extends from the platform and is insertable into a hole formed in the bone tissue. At least one rib extends from a surface of the post generally perpendicular to the axis of the post, the rib positioned intermediate the platform and a distal end of the post and establishing an interference fit relative to the hole in the bone tissue to prevent withdrawal of the device from a hole in the bone tissue into which it has been inserted.